Where there are a large number of technical devices, a plurality of electronic subsystems are interconnected in a communication union, said subsystems being able to be attributed a wide variety of functions, for example sensors, actuators, switches, displays, measuring units, controller systems, monitor systems, monitoring and debug devices, etc. These may be permanently installed and connected up in the device—for example during production of the device—but may also be modularly exchangeable, be it during servicing or during regular operation.
The present invention relates particularly to measuring systems. Examples of such measuring systems, which are designed as coordinate measuring devices, can be found in WO 2005/017448, EP 2 270 425 or WO 2006/079604, for example. These measuring systems have a plurality of subsystems, specifically in the form of electronic linear and/or rotary position sensors for measured value capture that are in a communication relationship with a controller for the purpose of measured value evaluation and control of the measuring processes. These subsystems are usually arranged in a physical distribution on the device, which means that set up of the communication link between the subsystems has an associated corresponding level of wiring complexity. The subscribers to the communication are thus wired in order to set up the communication link and/or a supply of power, and the present invention therefore involves wired or line-connected communication rather than a wireless radio system with free-space transmission. Besides the position sensors, there may also be further devices, for example probes, measuring heads, sensors, e.g. for sensing ambient conditions such as temperature, etc., or else actuators such as axle drives, motorized swivel heads, display elements, etc. In order to keep down a wiring complexity, there is an attempt in the measuring machines to use as few communication links as possible, preferably just one communication link, for all devices involved. An attempt is also made to design the communication links advantageously, that is to say to avoid double line runs as far as possible, for example, these occurring many times when each subsystem has star-shaped wiring to the controller, for example.
Besides the subsystems described above, which are usually mounted on the measuring system permanently, exchangeable components may also be involved in the measurement, for example exchangeable measuring heads, measuring sensors, supplementary joints, optical sample heads, etc., which are conditioned for a wide variety of measuring tasks and are likewise involved in the device communication. Since they are exchangeable during operation or in the course of reconfiguration, the communication system also changes in this case. Servicing work and repairs may also require replacement of a subsystem in the communication system.
In the case of such measuring systems, the communication between the devices or subsystems, that is to say the subscribers of the communication system, is often effected using bus structures. By way of example, a bus structure—such as RS232, RS422, RS423, RS485 or else others—can be used for communication. A popular topology that is often advantageous for the local arrangement of the devices in the measuring system is a serial structure. In this structure, the subscribers are arranged one after the other and connected to the bus with just one cable between the devices in each case. In this arrangement, the subscribers often also include several of the same kind, e.g. several position sensors of the same type, which use the shared bus to communicate with a control unit, that is to say to transmit the position information they ascertain to the control unit, for example. For the purpose of simple storage and maintenance, the subsystems of the same kind usually have no difference whatsoever prior to installation into the measuring system, which means that they can be used at a wide variety of locations in the machine.
During application, however, it is important for the subsystems connected to the bus to be able to be distinguished and identified, even if they are the same kind of subsystems. In the case of coordinate measuring devices, it is essential to know during surveying, for example, which position sensor is used to sense which movement axis in the measuring system.
To this end, it is possible to use a device address, for example, which can be set on the subscribers. This address is often allocated only directly before or after installation of the subscriber, for example by means of DIP switches, coding connectors, electronic programming devices, etc. Such an approach is susceptible to error and time-consuming, however.
In the literature, other areas of technology have a few approaches for avoiding manual address allocation. By way of example,
U.S. Pat. No. 5,666,557 describes automatic addressing of peripheral devices in a data processing system using connector identifiers;
WO 98/03921 describes the automatic recognition of the order of devices of a network communication device on the basis of a pulse length of a supplementary signal;
WO 2004/039010 describes the setting of addresses for child devices by a parent device;
WO 2007/104668 and DE 10 2006 025 174 describe address allocation for driver assistance systems.
A common feature of all these known approaches is that the subscribers are allocated an address externally. Even in the case of the above approaches, this is complex and in many cases requires additional hardware—such as coding switches, coding connectors, additional connector pins, etc. The complexity for allocating this address, whether during production, startup or in the course of bus initialization, is also not negligible. In addition, allocation of incorrect addresses is a frequent source of error in measuring systems, specifically when components are exchanged during servicing. Transposed addresses of communication subscribers can cause not only malfunctions but also hardware damage.